Recently, home theater systems, which give home users the feelings of being at live performances realized as visual and audio performances in theaters such as cinemas, have come to have a high popularity among people. A home theater system for home use is generally designed such that plural speakers are arranged to surround a listening position, and this is known as a 5.1-channel surround system. However, such an audio surround system constituted by plural speakers is complicated in wiring and is troublesome in setup due to limitations regarding arrangement of speakers. In addition, the audio surround system needs a relatively large space for installation. For this reason, the conventionally-known audio surround system cannot realize a simple system configuration for users who are to enjoy multi-channel audio.
There has been provided a technology for reproducing in an artificial manner audio surround effects using a 2-channel stereo speaker system, and this is known as an audio virtual surround system. However, it suffers from various problems such as artificiality in audio reproduction, limitations of listening environments, absence of feeling of being at a live performance, and degradation of sound quality. Hence, it has not come to be the current standard in home audio sound systems.
Recently, there has been provided another technology using a panel-type speaker array apparatus in which virtual sound sources are formed at prescribed positions surrounding a listener. This technology is disclosed in Japanese Patent Application Publication No. 2003-510924, a document provided by Pioneer Co. Ltd. (which can be retrieved via the Internet; URL: http://www.pioneer.co.jp/press/release 366-j.html), and a document regarding digital sound projectors provided by 1 Limited Co. (which can be retrieved via the Internet; URL: http://www.1 limited.com/lib/sound_projector_japanese.pdf), for example.
The aforementioned panel-type speaker array apparatus is constituted using plural speakers that are arrayed on a panel surface in a two-dimensional manner. The audio surround system using the panel-type speaker array apparatus performs delay control in such a way that sounds emitted by speakers focus on a single point in space, thus forming sound beams. The sound beams formed are reflected by wall surfaces in prescribed directions so as to form virtual sound sources surrounding a listener, thus realizing a multi-channel audio surround system using a single speaker array arranged in front of the listener.
The aforementioned audio surround system using the panel-type speaker array apparatus is capable of freely forming plural sound beams traveling in prescribed directions in front of a panel surface, and, it can freely localize sounds at prescribed positions with respect to separate channels. However, it is necessary to arrange numerous speakers (e.g., 254 speakers) in a two-dimensional manner in order to realize sound beam control having high directivity, and each speaker needs an audio circuit. Therefore, the aforementioned audio surround system is very expensive. In addition, it has problems due to the large overall area of a speaker array of a panel-type shape and a low degree of freedom regarding layout and setup position when it is combined with a display.
In consideration of the aforementioned circumstances, it is an object of this invention to provide a space-saving multi-channel audio playback system having a good live performance effect.
It is another object of this invention to realize a cost-saving speaker array for use in the aforementioned multi-channel audio playback system.
It is a further object of this invention to provide an audio playback system that is capable of freely controlling virtual sound sources and sound localization by use of sound beams, which are distributed in a sectorial form and are produced by means of line array speaker units each having limited directivity control.